This disclosure relates to a method for producing steam generator tube walls consisting primarily of 9-12% martensitic chromium steels.
Tube walls are primarily used in steam generators of power plants that are heated with fossil fuels. In this regard, the tube walls surround a combustion chamber that is rectangular in most cases, as well as the gas flue which is arranged over it and in which are arranged heating surfaces that as a rule are made of tube coils. The individual tubes of the tube walls, which are formed of a welded tube-fin-tube combination, carry within them a working medium heated by means of the combustion of the fossil fuel and pass it on to further processes. In the case of the known welded tube walls, the materials 16Mo3, 13CrMo4-5 and 7CrMoVTiB10-10 (T24) and the T23 material approved by the ASME (American Society of Mechanical Engineers) are usually used. As a rule, these materials do not require heat treatment after the welding manufacture or processing of the tube walls.
The desire for steam generation with higher efficiencies which, among other things, help to reduce the emission of CO2 into the atmosphere, leads to an increase of the steam parameters of the steam generator as one of a number of measures. To achieve or realize higher steam parameters, i.e., higher pressures and temperatures of the steam working medium, 9-12% martensitic chromium steels such as the material X10CrWMoVNb9-2 (T92) are required as the tube wall material, since the materials used previously no longer meet the higher requirements. In every case, the steels to be used now require a heat treatment after the welding work. During production of the tube walls, extensive welding work is required both in the workshop as well as at the construction site or during assembly. Specifically, these include as they relate to the workshop and the construction site:
Workshop: Production and completion of the tube wall panels including all of the weld-on parts, production of wall openings and bends as well as the production of wall bends and corner bends for the corners of the tube walls inside the inclined winding, production of transition regions from the inclined tubing to the vertical tubing.
Assembly: Welding of the segment and panel joints, pressure part assembly joints at circumferential welds, including all of the necessary filling and sealing welds, joints at slotted fins (assembly slot) and sealing welds on sockets and sleeves in the region of wall penetrations, completion of weld-on parts on the walls.
The task of the present invention is to suggest a method for producing steam generator tube walls consisting primarily of 9-12% martensitic chromium steels, in which the production takes place in a more efficient and practical way. In particular, it is the task of the invention to suggest a method for producing steam generator tube walls consisting primarily of 9-12% martensitic chromium steels in the workshop and at the construction site that is defined by the following boundary conditions:                Minimization of the welding work and heat treatments at the construction site,        Concepts for structurally necessary welds at the construction site without subsequent heat treatment,        Concepts for structurally necessary welds at the construction site using an optimized local heat treatment strategy.        